The present invention relates a code reading apparatus for optically reading a code on a recording medium on which data about audio information and the like is printed/recorded as an optically readable code.
A code reading apparatus like the above one proposed by the assignee of the present invention is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 6-231466 (EP No. 0,670,555A1), which includes a dot code as a code obtained by printing/recording data about audio information, video information, text data, and the like on a printing medium such as a paper sheet in an optically readable form, and a code reading apparatus that is manually operated to scan the dot code to optically read it, and reproduces/outputs information such as original audio information.
FIGS. 9A and 9B show the physical format of the dot code.
A plurality of blocks 30 are two-dimensionally arranged side by side to form a dot code 31. Each block 30 is composed of a data area 32 in which part of data about audio information or the like which corresponds to one of the blocks obtained by dividing the data is present as a dot image made up of white or black dots, each corresponding to "0" or "1", in a predetermined form, makers 33, each having a predetermined number of consecutive black dots, arranged on the four corners of the block 30 to be used to detect a reference point for detection of the respective dots in the data area 32, and block address patterns 34 that include error detection or error correction codes and are arranged between the markers 33 to identify each block 30 when the above different blocks 30 are read.
Note that the lines drawn in the form of a matrix are imaginary lines expressing the matrix.
Assume that the size of the image sensing plane of a solid-state image sensing device of a reading apparatus is smaller than the overall size of a dot code having such a physical format, i.e., the whole dot code cannot be sensed by the solid-state image sensing device with one shot. Even in this case, if the address assigned to each of the above blocks can be read and recognized, the original data can be decoded from the data of the respective blocks on the basis of the addresses. Consequently, a large amount of data that cannot be expressed by a known one- or two-dimensional bar code can be held on a paper sheet or the like. This technique facilitates data transfer through media such as a paper sheet, and hence is expected to have a variety of applications that are not conceivable in the prior art.
The above code reading apparatus used in this case performs so-called pulse emission, i.e., repeatedly emitting light at predetermined intervals by using an illumination means such as an LED in read/scan operation. Since the exposure time in image sensing operation is substantially determined by the emission intervals, various problems in read operation due to the influences of camera shake and the like can be solved, thus providing advantages in read operation by manual scanning.
In a code reading apparatus of this type, since a compact battery is used as a power supply, a battery voltage detection function is indispensable as in other types of electronic devices using compact batteries.
In addition, an LED or the like used as the above illumination means and the solid-state image sensing device consume a large amount of current, and the current consumption of the apparatus sequentially changes in its operation sequence.
In general, when the battery voltage of an electronic device using a compact battery is to be detected, the degree of consumption of the battery is detected after the power is turned on, and the user is immediately warned of the detection result.
As shown in FIG. 10, the voltage of a battery 1 is monitored by a voltage detection circuit 2 through a power switch 14. When the monitored voltage becomes equal to or lower than a predetermined level, the voltage detection circuit 2 outputs an L-level signal. Upon reception of this signal, a system controller 3 warns the user of this state.
With this operation, the user can check the degree of battery consumption before he/she uses the electronic device.
In the apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 3-253828, a camera battery checking unit includes a battery voltage determination control means for operating a battery voltage determination means a lapse of a predetermined period of time after a shift from the operation mode to the standby mode.
According to this apparatus, even if a warning is displayed in the operation mode, when the battery is restored after a lapse of a certain period of time, the warning display is updated and erased in the standby mode. In addition, since long battery check intervals can be set in the standby mode, unnecessary consumption of power for battery checks can be prevented.
It is, however, not easy to directly apply a battery voltage detection function like the one shown in FIG. 10 to a code reading apparatus for optically reading a dot code like the one described above and reproducing/outputting the original audio information or the like for the following reason.
A code reading apparatus of this type consumes a large amount of current, as described above. In order to save power, therefore, this apparatus uses a sequence of setting a standby state before scanning and after the code is scanned and the audio information or the like is reproduced/output.
FIGS. 11A and 11B show the relationship between the operation state of the code reading apparatus and changes in battery voltage level.
As shown in FIGS. 11A and 11B, in the standby state, since the load is light, the battery voltage is maintained high. In the scan state, however, since various circuit systems for, e.g., illumination, image sensing, and signal processing, operate, the load becomes heavy, and the battery voltage is low. In the audio reproduction state, since only the circuit system for audio reproduction processing becomes a load, the load is lighter than that in the scan state.
Furthermore, in the scan state, owing to the operation sequence for the above circuit systems, a large change in current consumption instantaneously occurs.
That is, since the load in a code reading apparatus like the present invention greatly changes with time as compared with an apparatus like the camera disclosed in Jpn. Pat. Appln. KOKAI Publication No. 3-253828, the consumption state of the battery cannot be satisfactorily detected by a method like the one disclosed in this reference.
As described above, in a code reading apparatus of this type, the current consumption changes due to the contents of a sequence of processing, from scanning of a code to reproduction/output of audio information or the like, and hence the battery voltage changes in a time series manner. Owing to such a special circumstance, an intended object cannot be achieved by the simple method of detecting a battery voltage upon power-on as shown in FIG. 10 or the method disclosed in Jpn. Pat. Appln. KOKAI Publication No. 3-253828.